Help Building a speaker system with pi Zero, phat dac, stereo amp and 2 speakers static noise


#1

I’m hearing a lot of static noise just wondering if I’m doing something wrong, I’m using pi music box, airplay works better than playing music locally.


#2

it is strange that you would get different results depending which source you use… that seems to indicate that hardware wise, all is correct.

That said, I would touch up ALL the ground points on the Pi header, and everywhere else there are ground connections, to be sure. Your soldering looks pretty OK though.

The other thing I would avoid is to criss cross cabling, such as the wires you got going out the pHAT DAC, those that connect to the amp.

… hope this helps.


#3

Thanks a lot, I will sort out the cables from dac to amp so there aren’t cross cross and re do all earth points on the pi header when I get home.


#4

I finally had time to look at this and I have resoldered the earths and moved the earth down to the next earth pin and I’m only able to uncross one side of the cables from the dac due to the layout of pins being different. It does seem to have improved the quality. I wonder if it’s anything to do with the gain from the amps. It’s the i2c amp. Not sure how to set it up with a raspberry pi, adafruit a site has for Arduino but. Or a pi.

Do you think the gain might be set to high?

https://shop.pimoroni.com/products/adafruit-stereo-2-8w-class-d-audio-amplifier-i2c-control-agc


#5

hum, I’m not sure. The signal leaving the pHAT DAC is at line level and this picture seems to imply that is supported/expected at the input end.

You could try that type of connection, maybe, using the 3.5mm jack out on the pHAT, and see if results are different, but AFAIK the signal there is equivalent to that of the RCA landing.


#6

That said, the specifications for the amp does note that an output filter is unnecessary for wire length under 2"-4", which implies that in your case, you need some additional components.

… all of the diagrams and pics on the Adafruit site feature considerably shorter wire length than yours, so inferring from those 2 facts I would say you are outside the use case for a simplified setup that dispenses of signal insulation.


#7

Is it the speaker cables which need to be 2-4"? Or amp to dac cables? Or both all together?

I can mount the pi in between the speakers and shorten down the cables.


#8

I shortened the speaker cables and have found that the static is due to the pimusicbox os. I have put the volume within the pimusicbox web gui to 5% and now works fine but I still would like to add volume control to my build. Is it possible to add volume control via gpio pins? like a volume up and down buttons. or something through the amp 1c2 interface?

I need to sort out the cabling still but wanting the sort the volume out first.